Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus, such as circuit breakers. The disclosed concept also relates to error-proofing features for secondary disconnect assemblies for circuit breakers.
Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions.
In power distribution systems, for example, power circuit breakers, which are also commonly referred to in the art as air circuit breakers, are often mounted within a switchgear enclosure either individually or in combination with other switchgear (e.g., without limitation, circuit switching devices and circuit interrupters such as circuit breakers, contactors, motor starters, motor controllers and other load controllers). Generally, there are two types or categories (i.e., sizes or configurations) of power circuit breakers, a relatively larger “draw-out” design, and a relatively smaller “fixed” design. The “draw-out” variety of power circuit breaker is movable with respect to a draw-out frame, also known as a cassette, whereas the “fixed” variety of power circuit breaker is generally fixed in position. Draw-out and fixed power circuit breakers have secondary disconnect assemblies, which are generally similar in design.
The secondary disconnect assembly of a draw-out power circuit breaker, for example, typically includes a plurality of terminal blocks, a mounting structure (e.g., without limitation, an elongated DIN rail) for mounting the terminal blocks, a movable cradle assembly, and a plurality of accessory plugs movable with the cradle assembly to electrically connect and disconnect from the terminal blocks. Thus, the secondary disconnect assembly allows the customer to establish a plurality of secondary terminal connections, for example, to populate the circuit breaker with a variety of desired accessories or features. In this manner, the customer can relatively easily customize the circuit breaker for a particular application. In addition, the secondary disconnect assembly provides a convenient mechanism to safely perform a test, such as for example, testing the sequence of a circuit breaker control circuit or powering an installed accessory to test its function before the circuit breaker enters service. That is, the circuit breaker is movable among a CONNECT position corresponding to the circuit breaker being completely inserted or installed within the cassette and electric power being supplied through both the primary and the secondary terminal connections, a TEST position corresponding to the circuit breaker being partially drawn-out of the cassette and power being supplied through only the secondary terminal connections, and a DISCONNECT position corresponding to both the secondary terminal connections and primary connections being disconnected, for example, to permit the circuit breaker to be completely withdrawn from the cassette to inspect, modify or replace the circuit breaker.
The components of the secondary disconnect assembly must be suitably supported and accurately aligned and positioned to ensure proper interaction (i.e., mating; de-mating) of the secondary terminal connections for reliable operation of the circuit breaker. For example and without limitation, some accessories are polarity sensitive, and may be assembled to the circuit breaker in the field, by the customer. The accessories must be accurately installed, and the components of the secondary disconnect assembly must be disposed in the proper orientations, or the accessory could be destroyed.
There is room for improvement in electrical switching apparatus, such as circuit breakers and in secondary disconnect assemblies therefor.